Sound reproducing device



with little distortion.

Patented Nov. 28, 1944 SOUND REPRODUCING DEVICE Semi Joseph Begun, Cleveland, Ohio, assignor to The Brush Development Company, Cleveland, Ohio. a corporation of Ohio Application July 31, 1941, Serial No. 404,773

18 Claims.

My invention pertains to, sound reproducing devices and more particularly to reproducers for use with records which have been cut with a let.- erally undulating groove.

It has been recognized that the process of producing laterally cut records introduces for a recrd modulated by a sinusoidal frequencma plurality of constrictions in the width r the cut groove to the plane cutting surface of the cutter being always perpendicular to the axis of the unmodulated groove. The frequency of these constrictions is twice the frequency of the signal recorded on the record. When a stylus having a point of finite radius of proper size to fit in the unconstricted portions of the groove and in contact with both groove walls, traverses the constricted portions of the groove it is forced up,

and as the constriction passes, the stylus settlesback into the unconstricted portion of the groove.

This is termed the "pinch effect." For low signal frequencies the "pinch effect" probably does not introduce serious distortion in the reproduced signal but for higher signal frequencies it does. The distortion arises fromthe fact that the stylus does not maintain contact with both side walls of the groove at all times. At low frequencies the force of gravity on the stylus acts to maintain the stylus in engagement with both side walls. But at higher frequencies the force of gravity does not accelerate the stylus in a downward direction quickly enough, and the groove bottom drops away from the stylus as the record turns. thereby causing the stylus tip to rattle loosely in a higher and wider portion of the groove. This inability of the stylus tip to be always coupled to both walls of the groove may cause distortion in the reproduced signal.

It is an object of my invention to obviate the foregoing difficulties.

It is a further object of my invention to substantially obviate the results of the "pinch effect" to provide a device which will reproduce signals An object of my invention is to provide a reproducer structure which will follow the undulations in the record groovaover a wide frequency range and with substantially uniform response.

Another object of my invention is to provide a reproducer which is subject to movements in more than one plane and which will effectively convert movements in substantially only one plane into an electromotive force.

Afurther object of my invention is to provide a reproducer which will give substantially undistorted response even though subject to severe "pinch efl'ect" conditions.

Still another object of my invention is to pro vide a reproducer having a stylus system of low mass but suflicient stylus force for good response.

Another object of my invention is to provide a reproducer having a low stylus force on a record and having a substantial percentage of that force arising from a biasing force.

It is another objectof my invention to provide a reproducer having a low total stylus force on the record and having thelow total force arising from a combination of low stylus mass and a slight stylus biasing force.

A further object of my invention is to provide a reproducer which is responsive to stylus motions in substantially only one plane.

Other objects and a fuller understanding of my invention may be had by referring to the following detailed description and claims, taken in conjunction with the accompanying drawing in which;

Figure 1 is a plan view on a small scale of a I phonograph turntable and a pickup arm.

Figure 8 is an isometric view of another form of my invention, and

Figure 9 is an isometric view of still another A form of my invention.

My invention is adapted to be used with a I phonograph which is illustrated in Figure 1 as comprising a base ID, a turntable ll mounted on the base It and adapted to rotate with respect thereto, and a pickup arm l2 secured to the base l0 and adapted to pivot with respect to the base and with respect to the turntable H. Equipment such as a motor 9 to drive the turntable,

amplifiers, and other such equipment necessary to convert record undulations into music, speech, etc. may be mounted inside the base ID. A phonograph record l3 may be mounted on the tumtable I I and as the turntable rotates the continuous spiral undulatory groove H which is on the and tear on the recordand stylus, and the downmay be made or several slabs of Rochelle salt crystal l1 and I8 cemented together to form a "twister" unit. Electrodes l9 and 20 are pro-. vided on surfaces the crystal slabs I! and I8, and leads 2| and 22 are'electrically connected to the electrodes. the lead 2| engaging the electrode i9 and the lead 22 engaging the electrode 20. The unit I6 is illustrated unwaterprooted to show the internal. construction, and it is to be understood that the unit may be covered by one or more layers of a waterproofing material.

The transducer unit It is held in a receptacle 21 in the pickup arm i2 by means of damping pads 28 and 29, and by means of shims 28, and a sliding wedge 25. A screw 24 holds the wedge in place. The damping pad 28 is positioned at the top edge of the transducer unit it and is adapted to substantially prevent movement oi the top edge of the unit IS with respect to the pickup arm l2, and the damping pad 28 is positioned along the center portion of the transducer unit l8 and extends from the top pad 28 substantially to the bottom of the unit It thereby establishing a central neutral axis along the section line 3-3 which is substantially immovable. A resilient drive wire 30 which may be a flattened hollow tube or a. solid strip having greater width than thickness, is connected at one end to the bottom of the transducer unit l6 and at the other end to the stylus l5. Movement oi the stylus l6 due to the undulations in the groove 94 in the record I8 is in a direction substantially normal to the surface of the cutting plane 2-2. This movement causes a twisting of the transducer unit it about the neutral axis and establishes an electromotive force substantially in accordance with the motion of the stylus Hi. The electromotive force appears at the. leads 2i, 22 which extend through a slot 3| in a boss 32 to one end oi. an attaching clip 33. The attaching clip 83 is connected at its center to the wall 32 of the receptacle 21 by a screw 34, and a connecting wire 35 is attached to the other end of the attaching clip 33 thereby establishing an electrical connection between the transducer unit l6 and the wire 35. The connecting wire 35 extends back through the arm 12 and into the base ill where it is connected to an amplifier.

Connected to the other wall 38 of the receptacle 2] by means of screws 31 is a spring 38. The spring 38 is adapted to bias the stylus l toward the record l3. A damping pad 39 may be provided between the spring 38 and the stylus IS. The stylus point is subject to desirable lateral movements due to the undulations in the record groove, and is subject to undesirable vertical movements due to "pinch efiect. The drive wire 30 is shaped to have a stiiiness factor in a first direction which is sumciently high to effectively transmit the desirable lateral stylus movements to the transducer unit it, and to have a stiffness factor in a second direction which is sufficiently low to substantially prevent transmission of the undesirable vertical stylus movements to the transducer. In other words the drive wire is relatively rigid in a horizontal direcward bias provided by the springs and 38 causes the stylus to be coupled to both of the side walls 01 the record groove to prevent stylus chatter which causes distortion in the reproduced signal. Under stationary conditions the stylus force is a function of the effective or un-' balanced weight of the pickup arm. This weight will deflect the stylus drive wire 30 and the spring 38. The amount of deflection will be proportional to the effective weight and will establish in the resilient drive wire 30 and in the spring 38 a downwardly directed biasing iorce. Under operating conditions acceleration forces will arise from the "pinch eflect and from the eflective stylus and spring mass, and the acceleration forces will vary the stylus force. Care must be taken that the acceleration force oppositely directed to the biasing force does not exceed the biasing force. The ability of a pickup having no spring bias to follow the pinch effect" is substantially independent of the weight of the stylus. Accordingly, a stylus force arising from a spring bias between the pickup arm and the stylus will cause the stylus to more closely follow the record groove than a iorce arising directly from the pickup arm.

Several means for establishing the downward bias may be used. In Figure 2 two spring units 30 and 38 are, provided, one of which may be the stylus drive wire. In Figure .3 the spring bias is provided by'the drive wire 3!! alone, and in Figure 6 damping means may contribute to the bias provided by the drive wire 30. P

Figure 4 illustrates a device in which the transducer unit I6 is replaceably connected in a housing M by means of the top damping pad 28 and a bottom damping pad 42, and the housing H is secured in the receptacle 2'! by means of screws 43 which thread into the receptacle wall 32. A side plate 44 (Figure 5) is connected to the side of the housing It by means of screws 45, and a bottom plate 46 having a hole through which the stylus projects is connected to the housing 4| by means of screws 41. I

Figure 8 illustrates another form of my invention in which the stylus I5 is connected to the transducer unit l8 by means of a plurality of wires 50, it which are arranged to brace each other in a horizontal direction to efiectively transmit the horizontal stylus motion to the transducer unit l6, and to provide vertical flexibility to substantially prevent the transfer of vertical stylus motion to the unit it. The wire 50 is looped around the top of the stylus l5 and is attached to a band 52 connected to the crystal unit I6, and the wire BI is looped around near the bottom of the stylus lb and is also connected to the band 52. Solder or other connection means maybe provided to connect the wires 50, 5! to the stylus l5. Vertical movement of the stylus l5 will cause the wires 50, 5! to bend, but horizontal movement in the direction of the arrow will cause a tension to be put in one side or the other of each of the wires 50, 5! thereby twisting thetransducer unit Ni. V

Figure 9 illustrates a waterproofed transducer unit 55 of the bender type with its associated leads 2|, 22, and the damping pad 63 which holds one end of the unit against movement. A connecting clip 54 attaches the stylus drive wire 30 to the crystal unit [8.

tion and is relatively flexible in a vertical direc- My pickup arm I2 (Figure 2) is provided with The "vertical flexibility permits the stylus changes in the details 01 into electrical impulses transmitting the lateral dition of a biasing force from the spring II without increasing the total stylus force to a'point where it is excessive. It may be a felt or ohamois piece which is adapted to conform slightly to the record-grooves to aid the stylus'in causing the arm to pivot with respect'to the record as the record turns.

Although I have described my invention with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example and that numerous construction and the combination and arrangement of parts may be resorted to without departing iromz the spirit and the scope or the invention as hereinafter claimed.

I claim as my invention:

1. In a pickup arm for use with a record having an undulatory groove, piezo-electric transducer means for converting a motion into an electromotive force, a stylus in engagement with said record and subject to motions from said undulatcry groove, driving meansdirectly connecting said stylus only to said transducer and tree from engagement with any other means and adapted to transmit said stylus motions to said transducer, said driving means providing a bias between said transducer means and said stylus to couple said stylus to said record groove to cause said stylus to follow said unduiatory groove substantially at all times.

2. In a pickup adapted for use with a record having a laterally cut groove, a Rochelle salt piezo-electric generator unit adapted to establish an,electromotive force upon being moved, stylus means directly connected to said generator unit and free from engagement with any other means but'having a with said record groove and subject to lateral movements and also subject to vertical, movements due to "pinch effect", said stylus means being comparatively rigid ina first direction to transmit said lateral movements to said transducer and comparatively flexible in a second di. rection to substantially prevent transmission 01' said vertical movements, and said stylus means establishing a spring bias between said generator supportingmeans to stylus point for engagement unit and said stylus point to maintain said stylus point in engagement with said record groove substantially continuously throughout the playing oi! the record.

3. Translating means cut record to convert undulations in the record comprising, a piezo-electric crystal unit which is bendable in a first direction and substantially non-bendable in a second direction, means for mounting said crystal unit, a stylus in engagement with said record and adapted to be actuated laterally by said undulations and also adapted tobe actuated substantially vertically, and driving means connecting said stylus to said crystal unit,- said driving means being comparatively stii! in a first direction and comparatively flexible in a second direction, said driving means in sad first direction efl'ectively movements oi said stylus for use with a laterallyto the said crystal unit to cause said crystal to bend in said first direction and generate an electromotive force, and said driving means in saidsecond direction and the substantially nonbendability of the crystal unit in said second direction co-operating to substantially prevent the said vertical actuations oi the stylus mm bending the crystal unit to prevent the generation oi an electro-motive force for vertical movements or the stylus.

4. Translating means ior use with a record to convert undulations in the record into electrical impulses comprising, supporting means, a Rochelle salt type crystal unit having a first ands second edge portion and having one oi said edge .portions restrained by said supporting means over substantially its I entire length, and having the other or said edge portions restrained by said establishaan axis substantially normal to the plane onsaid record, said unit being adapted to establish an electromotive force upon being actuated about said axis stylus means in engagement with said record and sub- Ject to desired motions in a first direction resulting from said record undulations and to undesired motions in another direction, means for connecting said stylus means to one of said edge portions or said unit to actuate said unit about said axis as, said stylus is moved in said first direction by the undulations in the said record, said connection means being flexible to reduce the transmission of the undesired motions to said crystal unit and to reduce the force on the stylus.

5. In a pickup unit adapted to be connected to a pickup arm and adapted a record having undulatory grooves, a transducer unit connected to said arm and'adapted to establish an electromotive force upon being actuated,

stylus means adapted to engage said record and subject to movement due to;v said undulatory grooves, first and secondilexible driving means connected to said stylus means-and to said transducer unit, meansproviding for movement of said stylus with respect to said transducer unit in a direction substantially'perpendicular to said record, and said first and said second driving means mutually bracing each other to cause a lateral movement oi said stylus to actuate said transducer unit.

6. In a pickup arm having a flexible stylus adapted to engage a surface and partially support said pickup arm on said surface, shoe means connected to said pickup arm and adapted to engage said surface and cooperate with said flexible stylus to support said pickup arm.

7. In a pickup arm pivotal with respect to and for use with a revolvable record having a continuous spiral undulating groove: an electromechanical transducer means-including flexible stylus means connected to said pickup arm and in engagement with said continuous spiral undulating groove and adapted to change the undulations of said first and said second driving' unit h ,tobe actuated by said groove into a varying electrical potential. and guide means connected to said pickup said spiral groove,

, with said record, said ment with the undulatory grooves 01 said record and subject to lateral and vertical motions, driving means connected to said stylus and connected to said transducer, said stylus and said driving means being adapted to transmit motions from said undulatory grooves to said transducer, said driving means eflectively transmitting lateral motions to said transducer and reducing the amount of vertical movement which is transmitted to said transducer, and shoe means connected to said pickup arm and in engagement shoe means and said stylus means cooperating to cause said pickup arm to pivot with respect to said record. I

9. In a pickup arm pivotal with respect to and for use with a record having a continuous spiral groove; a vertically flexible stylus means connected to said pickup arm and in engagement with-said continuous spiral groove for only partially supporting the unbalanced weight of said pickup arm, and shoe means having a conformable portion connected to said pickup arm and in engagement with said record, said conformable portion of said shoe means engaging and extending over several turns of said spiral groove and cooperating withsaid stylus means to support the said unbalanced weight of said pickup arm and to cause said pickup arm to pivot with respect to said record. t

10. A pickup arm pivotal with respect to and for use with a record having a series of undulatory grooves comprising, an electromechanical transducer connected to said pickup arm and adapted to establish an electromotive force substantially in accordance with motions in a first direction, stylus means relatively stiii in said first direction and relatively flexible in a second direction in engagement with the undulatory grooves of said record and in engagement with said transducer, and adapted to transmit forces according to motions in said first direction from said undulatory grooves to said transducer, said stylus means bending in said second direction to reduce the transfer or iorces according to motions in said second direction, and shoe means connected to said pickup arm and in engagement with said record, said shoe means and said stylus means cooperating to support said pickup and to cause said pickup arm to pivot with respect to said record.

ll. Translating means for use with a record to convert undulations in the record into electrical impulses comprising, a Rochelle salt type crystal unit, means for mounting said unit to establish an axis which is perpendicular to the surfaceoi said record and about which the said unit is adapted to twist to generate an electromotive iorce, stylus means in engagement with said record and connected to said unit and adapted to twist said unit as said undulations in said record cause said stylus means to move, and mechanical means for establishing a bias to couple said stylus to said record, and damping means connected to said mounting means and in engagement with said stylus means for damping the vertical movements thereof.

12. Translating means for use with a laterally cut record to convert undulations in the record into electrical impulses comprising, a piezo-electric crystal unit which is bendable in a first direction and substantially non-bendable in a second direction, means for mounting said crystal unit, a stylus in engagement with said record and adapted to be actuated laterally by said undulations and also adapted to be actuated substantially verticaliy, and driving means supporting said stylus means irom and directly connecting said'stylus to said crystal unit, and said driving means being free from engagement with other supporting means, said drivingmeans being comparatively still in a first direction and comparas tively flexible in a second direction, said driving means in said first direction eflfectively transmitting the lateral movements oi said stylus to the said crystal unit to cause said crystal unit to bend in said first direction and generate arr electromotive force, and said driving means in said second direction and the substantially non-bendability of the crystal unit in said second direction cooperating to substantially prevent the said vertical actuations oi the stylus from bending the crystal unit to prevent the generation of an elec tromotive force for veritcal movements of the stylus, and damping means in engagement with the driving means for damping the vertical movements oi the driving means.

13. Translating means for use with a record to convert undulations in the record into electrical impulses comprising, supporting means, 9. Bochelle salt type crystal unit having a first and a second edge portion and having one of said edge portions restrained by said supporting means over substantially its entire length, and having the other of said edge portions restrained by said supporting means to establish an axis substantially normal to the plane of said record, said unit being adapted to establish an eiectromotive force upon being actuated about said axis, stylus means in engagement with said record andsubject to desired motions in a first direction resulting from said record undulations and to undesired motions in another direction, means for connecting said stylus means to one of said edge portions of said unit to actuate said unit about said axis as said stylus is moved in said first direction by the undulations in the said record, said connection means being flexible to reduce the transmission of the undesired motions to said crystal unit, and damping means connected to said supporting means for damping the movements 0! said connection means in the direction of the desired movement.

14. In a pickup arm having flexible resilient stylus means including a tip portion adapted to engage a surface, said stylus means being adapted to partially support said pickup arm on'said surface, shoe means directly connected to said pick up arm and adapted to engage said surface and cooperate with said flexible stylus means to supfirst direction and also subject to undesirable motions in a second direction, and drive means comprised of a flattened hollow tube connected to said stylus and to said transducer for transmitting the stylus motions to the transducer, said flattened hollow tube being oriented to more effectively transmit the desired motions and less effectively transmit the undesired motions, said stylus means and said drive means from the point of engagement between said stylus tip and a record to the point where said drive means engages said transducer means being free from engagement with any other means.

17. In a pickup arm pivotable with respect to and for use with a record; a piezoelectric transducer connected to said arm, stylus means having arecord engaging tip and including flexible resilient drive means directly connecting said tip to said transducer and free from engagement with other supporting means, said stylus means being adapted to engage said record to support only a portion or the unbalanced weight of said pickup arm, and other resilient means connected to said pickup arm and in engagement with said stylus means for supporting a portion of the unbalanced weight of said pickup arm without stylus means when in engagement with a surface partially supporting the unbalanced weight of said pickup arm and stressing said fragile crystal, and auxiliary resilient supporting means connected to said pickup arm for supporting the remainder oi the unbalanced weight of said pickup arm without stressing said fragile crystal.

' SEMI JOSEPH BEGUN. 

